NAME

       dlangt.f -

SYNOPSIS

   Functions/Subroutines
       double precision function dlangt (NORM, N, DL, D, DU)
           DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest
           absolute value of any element of a general tridiagonal matrix.

Function/Subroutine Documentation

   double precision function dlangt (characterNORM, integerN, double precision, dimension( * )DL,
       double precision, dimension( * )D, double precision, dimension( * )DU)
       DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest
       absolute value of any element of a general tridiagonal matrix.

       Purpose:

            DLANGT  returns the value of the one norm,  or the Frobenius norm, or
            the  infinity norm,  or the  element of  largest absolute value  of a
            real tridiagonal matrix A.

       Returns:
           DLANGT

               DLANGT = ( max(abs(A(i,j))), NORM = 'M' or 'm'
                        (
                        ( norm1(A),         NORM = '1', 'O' or 'o'
                        (
                        ( normI(A),         NORM = 'I' or 'i'
                        (
                        ( normF(A),         NORM = 'F', 'f', 'E' or 'e'

            where  norm1  denotes the  one norm of a matrix (maximum column sum),
            normI  denotes the  infinity norm  of a matrix  (maximum row sum) and
            normF  denotes the  Frobenius norm of a matrix (square root of sum of
            squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.

       Parameters:
           NORM

                     NORM is CHARACTER*1
                     Specifies the value to be returned in DLANGT as described
                     above.

           N

                     N is INTEGER
                     The order of the matrix A.  N >= 0.  When N = 0, DLANGT is
                     set to zero.

           DL

                     DL is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) sub-diagonal elements of A.

           D

                     D is DOUBLE PRECISION array, dimension (N)
                     The diagonal elements of A.

           DU

                     DU is DOUBLE PRECISION array, dimension (N-1)
                     The (n-1) super-diagonal elements of A.

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           September 2012

       Definition at line 107 of file dlangt.f.

Author

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